This invention relates to tufting machines and more particularly to tufting machines for producing minimal pile height cut pile fabrics.
In conventional tufting machines an oscillating looper or hook cooperates with a reciprocating needle to form loops at the reverse side of the backing material penetrated by the needle. The fabric is supported by fingers extending forwardly from a needle plate and the needles pass between the fingers. In the production of loop or uncut pile the loops formed are released by the loopers and are drawn back toward the backing material by the needle. Thus, in general the height of the loops of uncut pile can be controlled to a very low or minimal height. In the production of cut pile fabric, however, the loops are not released by the barbed loopers or hooks, but remain thereon and are cut by an oscillating knife cooperating with each hook. At the loop seizing position the barb at the free end of the hook passes beneath the needle plate fingers so that the height of the backing material above the cutting edge of the hook, and thus the pile height, is determined by the geometry of both the hooks and the needle plate fingers.
The limitations imposed on the minimum pile height by the thickness dimensions of the fingers and barb are of relatively little consequence with regard to tufted fabric produced for use as floor coverings. However such limitations are of relevance in the context of machinery for use in the manufacture of ultra-low pile fabrics such as for upholstery fabrics, where the pile heights may be in the order of just a few millimeters.
In Beasley U.S. Pat. No. 4,193,359 a tufting machine is provided in which the bills of the hooks are arranged at substantially the same level as the needle plate fingers so as to produce low pile fabric. The pile height produced by this proposal, however, is limited since the base material still rests on the needle plate fingers and the pile height produced has a dimension substantially equivalent to the top of the needle plate fingers to the cutting edge of the hook.